Typically, as an electronic component, such as an LCD substrate or semiconductor wafer, is subjected to ultrafine surface processing, a transfer chamber 1 and processing chambers 2 of a manufacturing device for the electronic component are maintained in a vacuum, reduced-pressure or inert gas atmosphere in order to prevent undesirable chemical reaction or dust pollution on the surface of the electronic component.
As illustrated in one example of FIG. 1, in this manufacturing device, an opening 3 is provided approximately at the center of a bottom wall of the transfer chamber 1, for mounting the conveyance robot configured to take in or out a work between processing chambers, and a special conveyance robot is mounted on this opening 3 via a flange or the like in an air tight manner. Around the transfer chamber 1, the processing chambers 2 for performing various processing on the work and load lock chambers 4 for taking in or out the work from or to outside the device are arranged in a such a manner that they are communicable to each other via gates 5 as port openings. The transfer chamber 1 and these processing chambers 2 and load lock chambers 4 can be opened and closed while they are kept in an air tight state by an opening door operated by a valve, and various gas atmospheres in the processing chambers 2 and vacuum or reduced pressure atmosphere can be isolated from each other. And, in such a manufacturing device, the shape of the transfer chamber 1 is often hexagonal or octagonal, and the processing chambers and the load lock chambers 4 are arranged in a radial manner from the conveyance robot at the center. In this way, as the processing chambers 2 and the load lock chambers 4 are arranged radially, the conveyance robot is able to move the work from a load lock chamber to various processing chambers linearly.
As such a conventional robot as used in the transfer chamber 1, there is widely known a conveyance robot disclosed in Japanese Patent. Application Laid-Open 4-30447. This conveyance robot performs conveyance of the work by combining plural parallel link mechanisms, operating the link mechanisms together by a rotational force applied from the drive sources to drive side links, and moving a conveyance table on which the work is placed, back and forth between the transfer chamber and the processing chambers.
FIG. 2A is a plan view schematically illustrating a link mechanism provided in the conventional conveyance robot, FIG. 2B is a lateral view schematically illustrating one example of the conventional conveyance robot and FIG. 2C is a lateral view illustrating worn bearing and gear of the conveyance robot illustrated in FIG. 2B. The conventional conveyance robot has a conveyance arm 8 composed of a first parallel link mechanism 6 and a second parallel link mechanism 7 connected to each other and those mechanisms 6, 7 have drive side links and driven side links arranged parallel to each other. A conveyance table 9 for holding a work is provided at the tip end of the second parallel link mechanism 7. The first parallel link mechanism 6 and the second parallel link mechanism 7 are placed vertically shifted from each other in order to prevent interference from each other. The first parallel link mechanism 6 has a pair of long links 10, 11 supported by the base table 12 rotatable and a drive axis 13 as a rotational center of the drive side link 10 is connected to a drive motor (not shown) mounted under the base table 12. At the tip ends of the links 10, 11, a pair of links 14, 15 of the second parallel link mechanism 7 is connected rotatable thereto and the conveyance table 9 is connected to the tip ends of these paired links 14, 15 rotatably.
At a common short link 18a as a joint part of the links 10, 11 and the links 14, 15 of the first parallel link mechanism 6 and the second parallel link mechanism 7, gears 16, 17 are provided engaging each other with a gear ratio of 1:1. The gear 16 is fixed to the link 10 as the drive side link of the first parallel link mechanism 6 and the gear 17 is connected to the link 15 that is one of the links of the second parallel link mechanism 7 and connected to the link 11 as the driven side link of the first parallel link mechanism 6. The base ends of the links 14, 15 of this second parallel link mechanism 7 extend beyond the respective gears 16, 17 and are connected by the short link 18b rotatably.
In this configured conventional, conveyance robot, the drive axis 13 is rotated by the drive motor (not shown) thereby to rotate the link 10 as the drive side link of the first parallel link mechanism 6 and in conjunction with this rotation, the first parallel link mechanism 6 rotates by the same rotational angle as that applied to the link 10. This rotational angle of the first parallel link mechanism 6 is transmitted to the link 15 as the drive side link of the second parallel link mechanism 7 via gears 16, 17 that engages with same gear ratios, and the link 15 rotates by the same rotational angle in the direction opposite to the rotational direction applied to the link 10. In conjunction with this rotation of the link 15, the second parallel link mechanism 7 rotates by the same rotational angle as that transmitted to the link 15.